1. Field
Embodiments of the present disclosure concern pipe joints for connecting a first pipe to a second pipe and, in particular, to coupling of pipes such as thin walled tubes.
2. Description of the Related Art
Connecting two pipes with each other is a common objective and diverse devices have been proposed to accomplish this objective. International Patent Publication No. WO 2007/002576 discloses fittings for use with different types of tubing. One such fitting of WO 2007/002576 includes a gripping member having a sharp tube indenting edge that provides a seal between the tube gripping member and the tube. Another such fitting of WO 2007/002576 includes a tube gripping member having a body indenting edge that provides a seal between the tube gripping member and a fitting body. However, this solution is not capable of use in the oil and gas industry, as the standards which apply for the oil and gas industry concerning the connection of pipes with each other require reusability of all single elements. This requirement is not fulfilled in the device disclosed in WO 2007/002576, as plastic deformation, such as an indentation, is experienced in one of the tubes.
Other solutions are disclosed in U.S. Pat. No. 4,844,517, European Patent No. 0309179, and European Patent No. 1065423. In U.S. Pat. No. 4,844,517, a nut member contacts a coupling union via mating threads, while the coupling union is connected to a tube via recesses and protrusions of the tube which are positioned in the grooves of the coupling union. During tightening, the nut member forces the coupling union to contact a sleeve member, which is attached to another tube via grooves and protrusions. However, this device has a drawback of being difficult to mount.
Similarly, in the solutions disclosed in EP 0309179 and EP 1065423, a plastic deformation, as in WO 2007/002576, is employed for achieving the sealing effect, which is not desirable for connection of pipes in the oil and gas industry.
Another pipe coupling is discussed in U.S. Pat. No. 3,889,989 that focuses on high pressure pipe couplings in which one end of a bored coupling body is externally threaded to receive a rigid nut. The body and the nut each have an internal tapering surface which is in contact with an asymmetrical bi-conical rigid bite-ring made of ductile metal. The ductile metal is compressed by ridges into circular grooves formed on the end of a pipe to be coupled. The bite-ring has, between its tapering sections, a central section that has a larger diameter than that of the tapering sections. The central section of the bite-ring incorporates a circumferential sealing lip which is arranged to bear against an end face of the coupling body.
This pipe coupling employs movement of the nut in relation to the coupling body. However, as above, plastic deformation, this time of the bite-ring, is used to achieve a fluid tight sealing between the respective elements.
Thus, while approaches to tightly couple a first pipe to a second pipe have been developed, each has drawbacks concerning fluid tightness and reusability. As such, these solutions do not satisfy the standards relevant in the oil and gas industry.